Suggestion for better TCAS logic
I am not a pilot, but have followed this mid-air accident closely. I have the following suggestion for the TCAS logic, and would like comments on this.
In my opinion, the flaw is that the TCAS software assumes that the other party will follow the RA. This could be improved upon. I suggest that if TCAS realises that the other aircraft is not following the RA, but rather moving opposite to it (for whatever reason):
- assume that the other aircraft will not follow any RA in this situation
- issue a reversing sense RA to the non-complying aircraft so that the RA is consistent with its actual vertical speed
- issue a corresponding RA to the complying aircraft to achieve maximum separation
This logic would have avoided the Überlingen mid-air as follows:
(1) First RAs issued (descend to B757, climb to Tu154)
(2) after several seconds both TCAS computers realise that the Tu154 is not complying, as it is in fact descending.
(3) The computers should now re-calculate the forecast for the altitude at the potential collision location of the noncomplying aircraft, the Tu154, assuming that the current vertical speed of the Tu154 is maintained. The result of this calculation would have been a projected altitude of somewhere between 34,500 and 35,500 feet.
(4) The computer now re-calculates the optimal RA for the B757, which would have likely been a reversal sense RA ("Climb, climb now").
(5) Issue both RAs: "Climb, climb now" to the B757 (possibly followed up with a "Increase climb, increase climb") and a "Descend, descend now" to the Tu154 (possibly followed up with a "Increase descend, increase descend").
(6) Now there would have been no more confusion for the Tu154 crew, and while the B757 pilots might have been sweating while following the reversal sense RA, a safe vertical separation would have been achieved.
OK, comments please. Note that I do agree with many other additional safety measures suggested, and this only one further suggestion. It would have helped in this case, but might it lead to a higher probability of accidents in other cases?
Profit Max.